I did some tweaking to my WIFI, such as setting to 20mhz, enabling LDPC (error correction) and Cyclic Delay Diversity (on the router) and that stabalised downloads on Epic game store at 49-52 mbps, but only when homeplugs upstairs are turned off. I think the performance is a lot better with multi connection downloads too ( I don't think most downloads are).
I still get some drops with multi threaded downloads when all homeplugs are on, but its not that bad.